I have read the other upgrade threads, and gotten most of the info I need. But, this is a big decision for me, and I don't want to regret my decision later. Currently shoot a d5100 with the kit 18-55, the 50mm 1.8, and the 70-300 4.5 to 5.6. I want better IQ including color depth and dynamic range, better low light performance, better AF acquisition on moving targets, and low light AF, and the ability to crop tighter with acceptable resolution. I have been saving my GAS fund, and reached the point where I can make an offer on a local private sale, and likely pick up a virtually unused (reportedly 157 clicks) D800 along with a Nikkor 24-85 f/3.5-4.5. I could get this, and also keep all my DX stuff for now. My goal is to have a "jack of all trades" system. I realize if I upgrade to that body, I will be limited by lack of good glass, and upgraded lenses will be expensive, and it will take longer to accumulate a proper lens assortment. Specific questions: Will I notice or care about the AA filter in the D800? Is this a stupid idea: I won't be able to afford a good long lens in FX format for a good while. Probably a year. Could I put the d800 in DX mode, attach my 70-300, and do as well or better than my d5100 for wildlife? I realize my skills may not justify an upgrade, but if my wallet does, that's the important thing. Right?